Automatic light exposure device for the graphic arts

ABSTRACT

The present device provides a means to automatically force photosensitive materials into close contact with either a negative or a positive depending upon what type of print is to be produced. In addition, the present device employs a mercury lamp as its light source because of its wealth of ultraviolet light. The present arrangement acts to keep the mercury lamp on at all times and to automatically expose the photosensitive materials to the mercury lamp for the proper amount of time only after the photosensitive materials have been forced into close contact with the negative (or positive). The negative and the positive will hereinafter be referred to as the transfer image means. Thereafter the lamp is automatically turned off and the member forcing said close contact between the photosensitive material and the transfer image means is released.

ilnite States Tobias atem [191 AUTOMATIC LIGHT EXPOSURE DEVICE FOR THEGRAPHIC ARTS Benson 355/113 Primary Examiner-John M. Horan [57] ABSTRACTThe present device provides a means to automatically forcephotosensitive materials into close contact with either a negative or apositive depending upon what type of print is to be produced. Inaddition, the present device employs a mercury lamp as its light sourcebecause of its wealth of ultraviolet light. The present arrangement actsto keep the mercury lamp on at all times and to automatically expose thephotosensitive materials to the mercury lamp for the proper amount oftime only after the photosensitive materials have been forced into closecontact with the negative (or positive). The negative and the positivewill hereinafter be referred to as the transfer image means. Thereafterthe lamp is automatically turned off and the member forcing said closecontact between the photosensitive material and the transfer image meansis released.

5 Claims, 2 Drawing Figures tumult/ AUTOMATIC LIGHT EXPOSURE DEVICE FORTHE GRAPHIC ARTS BACKGROUND In the graphic arts it has been understoodfor a long time that Diazo paper is very responsive to ultravioletlight. It is also well known that a mercury lamp provides a wealth ofultraviolet light and therefore it is the practice, if possible, to usea mercury lamp as the source of light to which to expose Diazo paper anda transfer image means. It has been found that rapid response of thelamp and uniformity of ultraviolet light require that the mercury lampremain illuminated, rather than having it switched off and on with eachexposure. In the prior art, it has been the practice to, first, placethe photosensitive materials over the transfer image means which islocated on a transparent table top and thereafter an edge sealedflexible blanket is clamped over the photosensitive layer and saidtransfer image means. After the materials, which are going to be exposedto the light, are clamped the space under the flexible blanket isexhausted to a low pressure so that the blanket is forced downwardtoward the transparent table top causing the photosensitive material andthe transfer image means to be in very close contact.

Further in the prior art, subsequent to the foregoing two steps, ashutter over the mercury lamp is opened and held open for the properperiod of exposure time. Finally the lamp shutter is closed in responseto the operator throwing a switch or by time actuation, the vacuum pumpis stopped in response to an operator throwing a second switch and theoperator unclamps and lifts the lid to remove the exposed photosensitivematerial. For the next exposure the procedure is repeated and of coursesuch a procedure requires constant attendance. The present systemprovides an automatic arrangement with additional advantages.

SUMMARY In the present system the operation is automatic. The lid has anedge sealed flexible blanket center which is supported around itperiphery and in the back by a rigid section. The blanket can befabricated from rubber or some other suitable flexible, sturdy material.Means are provided to exhaust any air lying under the blanket within theseal and the transparent glass or plastic table top with which it comesin contact in response to the lid being simply closed, so that the airpressure on the upper side of the blanket and the underside of the glassforces the blanket within the seal against the photosensitive paper,transfer image means and glass. When the lid is closed against thetransparent table top a switch turns on a vacuum pump and exhausts theexposure chamber (the space between the edge sealed flexible blanket andthe transparent top) so that the blanket is automatically underpressure. Thereafter, automatically, the shutter over the lamp is openedfor the desired exposure time after which it is automatically closed.When the light has been automatically turned off the vacuum pump isturned off and the lid is automatically lifted. A minimum amount ofattendance is necessary.

The objects and features of the present invention will be betterunderstood in view of the description hereinafter taken in conjunctionwith the drawings in which:

FIG. 1 is a pictorial view of the present invention;

FIG. 2 is a schematic wiring diagram of the control circuit.

Consider FIG. I wherein there is shown a pictorial of the light exposuredevice. In FIG. 1 there is shown a housing means 11 which is cut away"in the front and on the side to show some of the necessary members ofthe system. Hinged to the housing 11 there is shown a lid 13 which isspring-loaded by spring 15 to the housing so that if the lid 13 is notheld against the transparent table top 17, it will be returned to itsreleased position as shown in FIG. 1.

When the system is in the ready for operation stage" the power plug 21is connected into an electrical power source. Accordingly, there iselectrical power supplied to the switch 23. When the light exposuredevice is to be used, the switch 23 is turned on which turns onindicator light 25 and which supplies power to the switch 27. Next theoperator turns on switch 27 which supplies power to the control box 19,which in turn supplies some electrical power to the mercury lamp held inshutter box 29. Prior to the actual exposure step, the lamp isilluminated under partial power so that it can readily be turned on whennecessary, without experiencing a start-up delay, and in addition whichstate does not consume full energy when the system is idling.

When the system is first turned on the mercury lamp will receive fullpower but shortly thereafter, it will be subject to partial power; i.e.,during the idling period as will be more fully explained hereinafter. Atthe same time, in addition to turning on the lamp to partialillumination, the fan 31 is turned on to keep the housing cool and thiseliminates damage from overheating.

Let us now assume that there is to be an exposure of Diazo paper (orsome otherphotoresist coated or photosensitive paper, offset plate, silkscreen, or a circuit to be etched) with a transfer image means. In suchcircumstances the photosensitve material with its sensitive side down,would be placed on top of the transfer image means to form the exposurepackage 33 shown in FIG. 1 lying on the transparent table top 17.Thereafter the lid 13 will be closed against the transparent table top17 causing the lid switch 35 to close. It should be noted that theunderside of the lid is made up of a blanket 41 to which there isattached a seal 42. When the lid switch 35 closes the vacuum pump 37 isturned on and the air is exhausted from the exposure chamber; i.e., theair lying under the blanket 41 within the seal 42 and the transparenttable top through the tube 39 whose opening can be seen in the flexibleblanket section 41.

When the vacuum pump has exhausted the exposure chamber, the section ofthe blanket 41 within the seal 42 will be forced down to insure a closecontact between the elements of the exposure package 33 and thereafterthe shutter motor 43 is turned on. The shutter motor 43 is a stall-typemotor such as a fractional horsepower geared motor manufactured and soldby Brevel Corporation. The motor 43 has its shaft 45 turn therebylifting the shutters 47 of the shutter box 29. Accordingly, the mercurylamp housed in the shutter box 29 transmits light to the exposurepackage 33. The lamp may be providing maximum illumination if desired bythe operator as will be explained in the discussion of FIG. 2.

When the vacuum pump has effected the proper vacuum in the exposurechamber, two additional automatic steps take place. First a timingdevice is turned on to provide a control signal at the end of theexposure time so that the shutters 47 will be closed at the end of theselected time and secondly the mercury lamp is subjected to fullelectrical power to thus provide maximum intensity light. The timer andthe means for providing the full power to the lamp are held in thecontrol box 19 and will be discussed in conjunction with the discussionof FIG. 2.

When the timer has reached its full time, the shutter motor 43 (whichwill be in a stalled mode) will be turned off and the shutters 47, whichare spring-loaded as shown, will be returned to their closed position(shown in FIG. 1). After closure of the shutters and only after suchclosure, the vacuum pump will be turned off, which in conjunction with anormally open solenoid valve, opening to the atmosphere in T connectionwith the vacuum tube, will cause the force which kept the lid closed tobe removed and the lid will be returned to its released position underthe urging of spring 15.

It becomes apparent that the exposure package 33 can be quickly removed,another put in its place and the lid closed to start the process overagain. Once the lid 13 is closed the process is automatic and involvesno operators in attendance or throwing switches or opening and closingof clamps, etc.

Consider FIG. 2 which is a schematic wiring diagram of the circuitryfound in control box 19. In FIG. 2 there is shown the power plug 21which provides electrical power from a source, through the fuse box 51to the switch 23 which we discussed earlier. When the switch 23 isclosed it causes the indicator lamp 25 to be illuminated as discussedearlier and provides power to switch 27. In addition one side of thepower line starting at terminal 53 is connected by line 55 to lines 57,59 and 61, and through switch points 63 to lines 65 and 67.

If the circuits connected to the lines 57, 59, 65 and 67 are traced outit will be found that these circuits are not completed, at this time, toline 69 which returns to the other side of the power line at terminal71. However, there is a completed circuit connected to line 61.Electrical current passes from terminal 53, along line 55, along line61, through the normally closed points 85, along the line 89 to line 73,through the normally closed points 75, along line 77 to energize relay79 and along lines 81 and 83 to line 69, thus completing the circuit.Accordingly, relay 79 is energized when switch 23 is closed.

It should be noted that when relay 79 is energized it closes thenormally open points 89 and 91. Relay points 89 are holding relay pointsand serve to keep relay 79 energized even if the normally closed pointsof the frame switch are opened (and provided that points remain closed).The system now awaits the closing of the switch 27 as mentioned above.

When the operator is going to actually use the machine he turns onswitch 27. With switch 27 closed electrical current will flow along line93, along line to energize the fan 31, along line 97 to the other sideof switch 27. Current also passes along line 93, along line 99, alongline 101 to energize the primary winding 102 of transformer 104, alongline 103 to the other side of the switch through line 97.

In addition electrical current passes along lines 93, 99 and 105 to thestarting module 107. The starting module 107 can be a voltage sensitiverelay, or a difference amplifier connected to a relay or any one of thehas a pair of normally closed terminals therein and a voltage sensitiveelement. When the voltage across the exposure (mercury) lamp 109 reachesa'eertain threshold, then the normally closed points 111 of the'startingmodule will open and the function should be apparent immediatelyhereinafter.

While the normally closed points 111 are closed there will be electricalcurrent along line 113 to energize relay 115 and return to the otherside of the line (line 69 via line 117). The energization of relay 115closes the normally open points 119 and their role will be explainedhereinafter.

Going back for a moment it will be recalled that the primary winding 102was energized and this in turn induced a voltage on the secondary 121.The voltage induced in the secondary 121 acts as a source voltage tosupply current along lines 123 and 125, through mer cury lamp 109, alonglines 127 and 129, through the impedance network 131 to the other sideof the secondary winding 121. The impedance network 131 is comprised ofa resistor and a capacitor. The capacitor limits the power to lamp 109and the resistor provides a discharge patch. The capacitive impedance ofimpedance network 131 is sufficiently high to subject the lamp to aboutone-half power. When the points 119 are closed the capacitor ofimpedance network 133 is added in parallel with the capacitor ofimpedance network 131 to reduce the overall impedance and thus subjectthe lamp to full power and obtain maximum illumination. This procedurealso permits the lamp to warm up to operation temperatures rapidly.After the full power is applied to the lamp and the voltage drop thereacross equals the threshold value of the voltage sensing element of thestarting module 107, the normally closed points 111 will be opened andthe relay 115 will be deenergized. When relay 115 becomes de-energizedthe points 111 drop out thereby cutting out the parallel impedance 133and thus reducing the power applied to lamp 109.

Thus far switches 23 and 27 have been turned on with the result that thelamp 109 is illuminated under half power, the fan 31 is operating andrelay 79 is energized. The system is involved in no other steps untilthe lid 13 (FIG. 1) is closed.

When the lid 13 is closed, the lid switch 35 (FIGS. 2 and 1) is closedand (FIG. 2) we find the normally open points 135 will be closed. Theclosing of points 135 provides current from line 73, through points 135,through points 91 to energize relay 137, and thereafter to line 69 vialine 83. When relay 137 is energized the normally open points 139 areclosed which provides current along line 57, through points 139 toenergize pump 37 and close the solenoid valve 141. It is necessary toclose valve 141 when pump 37 starts pumping because this valve opens thevacuum tube 39 to the atmosphere through a T connection when the valveis not energized and hence if it were not closed the vacuum pump wouldnot effectively exhaust the air from the exposure chamber. Thus when thevalve 141 and pump 37 are energized, the exposure chamber under theclosed lid will have the air exhausted therefrom. Now the vacuum pump 37and tube 39 have a pneumatically-operated vacuum switch 143 associatedtherewith and when a sufficient degree of vacuum has been obtained inthe exposure chamber, the switch 143 will close. The switch 143 isphysically located connected to tube 39 and can be a Bourdon tubeactuated switch manufactured by the Mercoid Company. When the switch 143closes, electrical current will pass along line 65, through switch 143,along line 145, through the normally closed points 147 of the shutterrelay 159 to the transformer 151. The transformer 151 is a step downtransformer and as can be seen in the schematic (FIG. 2), the power tothe shutter motor 43 is from a tapped position on the transformer.

Accordingly the shutter motor 43, which operates with a reduced appliedvoltage, is energized. As explained earlier, the shutter motor 43 is astall motor which operates to open the shutters covering the lamp 109and will stall and keep the shutters open for as long as energy isapplied to the motor. When the shutters 47 are opened they operate toclose the points 71. Accordingly the relay 79 is held energized throughpoints 85 and 71.

It should be recalled that during the idling period the lamp 109 hasless than full illumination. If the operator is desirous of only lowillumination he moves the manual switch 142 to the L (low) position asshown in FIG. 2. On the other hand, if the operator wants the lamp 109to be operated at maximum intensity he will move the switch 142 to the H(high) position. It should be noted that when the switch 142 is in thehigh position and the vacuum switch 143 closes, electrical current willpass along line 145, through points 147, along line 144, through the Hpoint of switch 142, through the normally open points 146 of thestarting module 107 to energize relay 115. When relay 1 is energized theoperation is as described earlier; i.e., points 119 will close toconnect the impedance network 133 in parallel with impedance network 131thereby applying full power to the lamp 109 and causing highillumination thereof.

When the lamp 109 is providing maximum illumination, additional coolingis required. This is accomplished by providing electrical currentthrough the H points of switch 142, through the lamp cooling blower 144to line 117 and back to line 69.

Further and simultaneously with the energization of the shuttermotor 43,and full illumination of lamp 109, current is passed along line 153 toenergize the timer motor 155.

The timer mechanism is a standard automatic reset timing mechanism suchas one manufactured and sold by Precision Timer Company. When the timerhas completed its time cycle, the points 157 will be closed which willenable current to pass along line 67, through relay winding 159 throughpoints 157 to the other side of the line (line 69). It follows that whenrelay 159 is energized the points 85 and 147 open thereby cutting offthe electrical current to the shutter motor 43 and the high intensityrelay 115. It will be recalled that with the shutters open; i.e.,shutters 47 (FIG. I) lifted, the points 71 will be closed.

Thus it becomes apparent that relay 79 will be deenergized only afterthe shutters 47 are closed. This arrangement insures that the lid 13will not be released until the shutters are completely closed. In otherwords, even though the timer has caused relay 159 to be deenergized, thepump 37 and solenoid valve 141 will remain energized (thus keeping thelid closed) until the shutters 47 close. This is a safety measure forthe operator; i.e., the lid will not pop up while the mercury lamp is ina position to send light through the transparent table top and injurethe operators eyes. This arrangement also avoids partial exposure of theexposure package under no vacuum" conditions.

When the shutters 47 return to their closed position, the points 71 openand relay 79 drops out, thereby opening the points 89 and 91. In turn,relay 137 becomes de-energized causing points 139 to open. When points139 open, the electrical current to the vacuum pump 37 and valve 141 isinterrupted and thus the vacuum pump ceases to exhaust the exposurechamber while open valve 14] opens the exposure chamber to atmosphere.Accordingly the lid 13 is no longer forced down but is released andmoves upward under the urging of the spring 15.

The functions of switch 63 and switch 72 are to circumvent the automaticfeatures of the unit when desired. When switch 63 is opened manually theexposure is delayed because the timer is taken out of the system. Ifswitch 72 is manually closed the vacuum can be maintained even thoughthe exposure time is finished.

I claim:

1. An automatic light exposure device comprising in combination: housingmeans; transparent means disposed to form the top of said housing means;lid means movably secured to said housing means and formed and disposedto fit over and come in contact with said transparent means; flexiblemeans disposed to form a substantial portion of the side of said lidmeans which comes in contact with said transparent means; vacuumeffecting means connected to said flexible means to effect a substantialvacuum between said transparent means and said flexible means inresponse to said lid means coming in contact with said transparent meansthereby providing a force against said flexible means toward saidtransparent means; lamp means; shutter means disposed to cover said lampmeans when closed and to expose said lamp means when open; shuttermoving means connected to said shutter means to cause said shutter meansto open and close; timing means; switch means disposed on said lid meansto be switched when said lid means comes in contact with saidtransparent means; vacuum detecting means connected to said vacuumeffecting means to detect said substantial vacuum and in responsethereto to provide a signal for activating said shutter moving means;and control circuitry means connected between said switch means, saidvacuum detecting means, said shutter moving means, said timing means,and said vacuum effecting means whereby when said switch means isswitched said vacuum effecting means effects said substantial vacuum sothat said force causes said flexible means to come in close contact withsaid transparent means and whereby said vacuum detecting means providesa signal to cause said shutter moving means to move said shutter meansto expose said lamp means for a predetermined time, as determined bysaid timing means, and whereby at the end of said predetermined timesaid shutter moving means closes said shutter means and whereby saidvacuum effecting means terminates effecting a vacuum to remove saidforce from said flexi ble means.

2. An automatic light exposure device according to claim 1 wherein saidcontrol circuitry includes a lamp power circuit which causes said lampto be illuminated to less than maximum intensity when said shutters areclosed and alternatively illuminated to maximum intensity when saidshutters are open.

atmosphere when said vacuum pump is operating and to open said valve tothe-atmosphere when said vacuum pump is not operating.

5. An automatic light exposure device according to claim 1 wherein thereis further included means to lift said lid whereby when said force isterminated said lid automatically lifts.

1. An automatic light exposure device comprising in combination: housingmeans; transparent means disposed to form the top of said housing means;lid means movably secured to said housing means and formed and disposedto fit over and come in contact with said transparent means; flexiblemeans disposed to form a substantial portion of the side of said lidmeans which comes in contact with said transparent meAns; vacuumeffecting means connected to said flexible means to effect a substantialvacuum between said transparent means and said flexible means inresponse to said lid means coming in contact with said transparent meansthereby providing a force against said flexible means toward saidtransparent means; lamp means; shutter means disposed to cover said lampmeans when closed and to expose said lamp means when open; shuttermoving means connected to said shutter means to cause said shutter meansto open and close; timing means; switch means disposed on said lid meansto be switched when said lid means comes in contact with saidtransparent means; vacuum detecting means connected to said vacuumeffecting means to detect said substantial vacuum and in responsethereto to provide a signal for activating said shutter moving means;and control circuitry means connected between said switch means, saidvacuum detecting means, said shutter moving means, said timing means,and said vacuum effecting means whereby when said switch means isswitched said vacuum effecting means effects said substantial vacuum sothat said force causes said flexible means to come in close contact withsaid transparent means and whereby said vacuum detecting means providesa signal to cause said shutter moving means to move said shutter meansto expose said lamp means for a predetermined time, as determined bysaid timing means, and whereby at the end of said predetermined timesaid shutter moving means closes said shutter means and whereby saidvacuum effecting means terminates effecting a vacuum to remove saidforce from said flexible means.
 2. An automatic light exposure deviceaccording to claim 1 wherein said control circuitry includes a lamppower circuit which causes said lamp to be illuminated to less thanmaximum intensity when said shutters are closed and alternativelyilluminated to maximum intensity when said shutters are open.
 3. Anautomatic exposure device according to claim 2 wherein said lamp is amercury arc lamp.
 4. An automatic exposure device according to claim 1wherein said vacuum effecting means comprises a vacuum pump with a tubeconnected thereto and a solenoid valve connected between said tube endatmosphere and wherein said control circuitry means is connected to saidsolenoid valve to close said valve to the atmosphere when said vacuumpump is operating and to open said valve to the atmosphere when saidvacuum pump is not operating.
 5. An automatic light exposure deviceaccording to claim 1 wherein there is further included means to liftsaid lid whereby when said force is terminated said lid automaticallylifts.